Set wgTranslateTranslationServices['TTMServer']['cutoff']

When not set, we see "Undefined index: cutoff" errors from
Translate/ttmserver/ElasticSearchTTMServer.php. Niklas suggested that
0.65 would be a reasonable value to use.

Change-Id: I138b22a0c23fd08372a51eb9ed6662a11a7fe155